基于放射性核素的沉积物源识别技术探索与优化——以红树林-海草床-珊瑚礁系统为例

Exploring and optimizing characterization of radionuclide fingerprint for tracking sediment source:Comparison of mangrove,seagrass,and coral reef ecosystems

物质来源是沉积学研究的关键问题。沉积地球化学是沉积学的重要研究手段,放射性核素在沉积地球化学中的应用探索仍较为匮乏。本研究利用高纯锗γ谱仪同时测量红树林、海草床、珊瑚礁三大典型生态系统的沉积物中天然放射性核素(^(238)U、^(226)Ra、^(228)Ra、^(40)K),分析3种生态系统的沉积物中放射性核素分布特征,探索基于放射性核素的一维视角下活度特征、二维视角下核素对与活度比值、三维视角下三角图解的指纹表征技术,识别沉积物中不同物质的来源,并尝试推广至中国不同海域。本研究强调三维指纹表征技术—基于核素活度的^(238)U-^(232)Th(^(228)Ra)-^(40)K/10三角图解可以综合展示3种放射性核素的活度大小、组成比例、空间分布等信息,指出^(238)U-^(232)Th(^(228)Ra)-^(40)K/10三角图解可能是沉积物中物源识别的一种优化方法,可为沉积地球化学研究中的现有代用指标工具库提供有益补充。

Sediment source is a key issue in sedimentology.Although sediment geochemistry is an important tool in sedimentology,the explorations and applications of radionuclides in sediment geochemistry are still limited.In this study,naturally occurring radionuclides(^(238)U,^(226)Ra,^(228)Ra,and ^(40)K)in sediments were simultaneously measured using a high-purity germaniumγ-spectrometer in three typical ecosystems of mangrove,seagrass,and coral reefs.The distribution characteristics of radionuclides in sediments from the these ecosystems were discussed in one-dimensional view of activity level,two-dimensional view of radionuclide pairs and activity ratio,and three-dimensional view of ternary diagram of radionuclides to identify distinct sources of sediments.Ternary diagram of ^(238)U-^(232)Th(^(228)Ra)-^(40)K/10 in sediments was applied in the China different seas for tracking distinct sediment sources.This study emphasized that the three-dimensional view of ternary diagram of ^(238)U-^(232)Th(^(228)Ra)-^(40)K/10 comprehensively exhibited the information of activity level,composition,and spatial distribution area of radionuclides.In conclusion,ternary diagram of ^(238)U-^(232)Th(^(228)Ra)-^(40)K/10 may be an optimized method for source identification in sediments and provide a supplement to the existing tools of geochemical proxies.